Abstract The Western States Node's (WSN) research agenda for the National Drug Abuse Treatment Clinical Trials Network (CTN) competing renewal tests interventions to fill gaps in the Addiction Care Cascade, where progressively fewer people with drug use engage in treatment, receive pharmacotherapy, are retained in care, and experience sustained recovery. The Node proposes to continue the successful partnership between Oregon Health & Science University (OHSU; Todd Korthuis, MPI) and University of California San Francisco (UCSF; James Sorensen, Co-I), and adds Stanford University/Palo Alto VA (Keith Humphreys, MPI) to the collaboration. Six diverse health systems participate in WSN: 1) OCHIN, 2) The Palo Alto VA and national Veterans Healthcare Administration, 3) The OHSU health system, 4) Stanford Hospital and Clinics, 5) ProtoCall Services, Inc., and 6) Health Share and Trillium Medicaid managed care organizations. The WSN tests novel interventions that expand access to medications for opioid use disorder (MOUD). The overarching goal of the WSN's competing renewal application is to conduct collaborative research within the CTN that fills gaps in the Addiction Care Cascade and thereby enhances the lives of people living with drug use disorders. Our Addiction Care Cascade-focused research agenda developed through conversations with diverse investigators and stakeholders including people who use drugs. Two research themes (medication trials and hybrid implementation trials to close gaps in the Addiction Care Cascade) provide four examples of CTN studies that could help close treatment gaps. In Research Theme 1 (medication trials), Medication Trial 1 targets people with OUD who are not interested in currently available MOUD and randomizes them to receive long acting oral hydromorphone versus facilitated referral methadone or buprenorphine to improve engagement and retention in treatment. Medication Trial 2 is a multisite phase 3 trial of mirtazapine versus placebo for people with methamphetamine use disorder to reduce methamphetamine use. In Research Theme 2 (hybrid implementation trials), two trials compare strategies to enhance engagement and retention on MOUD. Hybrid Effectiveness-Implementation Trial 1 is a cluster- randomized trial of telephonic + mHealth behavioral support services to improve retention on buprenorphine in primary care. Hybrid Effectiveness-Implementation Trial 2 tests a telementoring peer support intervention versus weekly peer supervision to improve peer success in engaging and retaining people who use drugs in treatment. We suffuse this research agenda with the Node's infrastructure and expertise in vulnerable populations, health systems, electronic health records research, data science and clinical trials management. WSN offers these resources to the CTN network for use in future CTN protocols. Finally, WSN continues to use the CTN as a platform for training, dissemination, and research applications.